What is a Map Projection?

A map projection is a method used to represent the curved surface of the Earth on a flat plane, such as a sheet of paper or a computer screen. Since the Earth is a three-dimensional object (a roughly spherical shape), it’s impossible to accurately represent its surface on a two-dimensional map without some distortion. A map projection essentially “flattens” the globe, and different projections preserve or distort certain aspects of the Earth’s surface in various ways.

Key Types of Distortion in Map Projections:

When a three-dimensional globe is projected onto a two-dimensional surface, it can cause distortion in several ways:

• Area: The size of regions can be distorted, making some areas appear larger or smaller than they are.
• Shape: The shape of areas can be distorted, making them look stretched or compressed.
• Distance: The distances between locations can be distorted, which might make travel or measurements inaccurate.
• Direction: The angles and direction between points can also be distorted.

Common Map Projection Types:

There are various map projections, each with its own way of representing the Earth’s surface while prioritizing the preservation of certain properties. Some of the most common ones include:

1. Mercator Projection:
   • Description: One of the most widely known projections, it represents the Earth as if it were a cylinder. It preserves angles and shapes (making it useful for navigation), but distorts area, especially near the poles.
   • Use: Often used in navigation charts and world maps.
   • Distortion: The area distortion increases as you move away from the equator. For example, Greenland appears much larger than it actually is.
2. Robinson Projection:
   • Description: A compromise projection that aims to minimize distortion in area, shape, distance, and direction. It’s often used for world maps to provide a visually appealing representation of the entire globe.
   • Use: Used for general-purpose world maps.
   • Distortion: While the Robinson projection minimizes distortion in all aspects, it doesn’t preserve any one property perfectly.
3. Gall-Peters Projection:
   • Description: A cylindrical projection that emphasizes the accurate representation of area. It distorts shapes and angles but shows countries in their correct size relative to one another.
   • Use: Often used in educational settings to show a more accurate portrayal of the relative sizes of countries.
   • Distortion: It distorts shapes, especially near the equator, but shows land masses in a more proportional way.
4. Azimuthal (Planar) Projection:
   • Description: A projection that shows the Earth from a specific point (often the poles), typically preserving direction from the center point.
   • Use: Used in polar maps or maps for air navigation, where distance and direction are important.
   • Distortion: Distorts areas and shapes as you move away from the center of the projection.
5. Conic Projection:
   • Description: A projection that represents the Earth as a cone placed over the globe, typically used for mid-latitude regions.
   • Use: Commonly used for maps of countries or regions that are spread over a large area in the mid-latitudes (like the United States).
   • Distortion: Distortion increases as you move further from the standard parallel (the line of latitude where the cone touches the globe).
6. Sinusoidal Projection:
   • Description: A pseudo-cylindrical projection that represents the Earth with straight, equally spaced lines of longitude and curved parallels.
   • Use: Often used in thematic maps to show global distributions.
   • Distortion: Maintains equal area but distorts shape and distance.

Choosing the Right Map Projection:

The choice of map projection depends on the purpose of the map and which properties (area, shape, distance, direction) need to be preserved or minimized. For example:

• If accurate area is important (e.g., for population density maps), a equal-area projection like the Gall-Peters projection may be chosen.
• For navigation, where angles and directions need to be preserved, the Mercator projection may be more appropriate.
• For general-purpose world maps where a balance of all properties is desired, the Robinson projection is often used.

The National Geographic Society Changed to the Winkel Tripel Projection

In 1998, the National Geographic Society (NGS) switched from the Robinson projection to the Winkel Tripel projection as its standard for world maps. The main reason for this change was to improve the balance between size, shape, and distance accuracy, reducing distortions that are inevitable in any two-dimensional representation of a three-dimensional Earth.

Limitations of the Robinson Projection

The Robinson projection, adopted by NGS in 1988, was designed as a compromise between different types of distortions. It offered a visually appealing map with less shape distortion near the poles compared to the commonly used Mercator projection. However, it still suffered from size distortions, especially near the edges of the map. Landmasses near the poles appeared stretched, and some distances were misrepresented, leading to inaccuracies in global geography.

Why Switch to the Winkel Tripel?

The Winkel Tripel projection, developed by Oswald Winkel in 1921, was chosen as the new standard because it provided an even better balance of distortions. Its key advantages include:

1. Less Area Distortion – Countries and continents appear more proportional in size, reducing the exaggeration of landmasses near the poles.
2. Reduced Shape Distortion – The Winkel Tripel maintains a more natural look for landmasses, avoiding the stretched appearance of the Robinson projection.
3. Better Distance Representation – While not perfect, distances on the Winkel Tripel are more accurate compared to the Robinson projection.

Overall, the National Geographic Society chose the Winkel Tripel projection because it provided a more accurate and visually balanced depiction of the world, making it a superior choice for educational and general-use maps.